DESCRIPTION OF REARED EGGS AND YOUNG LARVAE OF 

 THE SPOTTED SEATROUT, CYNOSCION NEBULOSUS 



William A. Fable, Jr., Theodore D. Williams, and C. R. Arnold ' 



ABSTRACT 



Adult spotted seatrout, Cynoscion nebulosus, were induced to spawn in the laboratory by controlling 

 temperature and photoperiod. Development of eggs and larvae, reared at 25°C, is described to 15 days 

 after hatching. The pelagic, spherical eggs have a mean diameter of 0.77 mm, and usually contain one 

 oil globule averaging 0.22 mm in diameter. Hatching occurs about 18 h after fertilization. Standard 

 length at hatching is between 1.30 and 1.56 mm. Spotted seatrout average 4.4 mm standard length at 

 notochord flexion. The larvae, which were fed the rotifer, Brachionis plicatilis, tmd nauplii oiArtemia 

 sp., grew to about 4.5 mm standard length in 15 days. 



The spotted seatrout, Cynoscion nebulosus, is one 

 of the most important fishes to both recreational 

 and commercial fishermen in the Gulf of Mexico 

 and southeastern United States. In the Gulf it 

 ranks first in weight landed by sports anglers 

 (Deuel 1973) and seventh by weight taken com- 

 mercially (U.S. Department of Commerce 1975). 

 Despite its value, the eggs and youngest larval 

 stages have not been adequately described in pre- 

 vious literature. 



Four early works (Welsh and Breder 1923; Hil- 

 debrand and Schroeder 1928; Pearson 1929; Hil- 

 debrand and Cable 1934) provided descriptions of 

 spotted seatrout development. Welsh and Breder 

 (1923) described juvenile C. nebulosus as small as 

 28 mm, collected from North Carolina and 

 Chesapeake Bay waters. Hildebrand and 

 Schroeder (1928) illustrated a spotted seatrout 

 presumably 120 mm long, apparently from 

 Chesapeake Bay. Spotted seatrout from Texas as 

 small as 7.8 mm were described by Pearson (1929). 

 The most complete description of young spotted 

 seatrout was by Hildebrand and Cable ( 1934). The 

 smallest seatrout described by them was 1.8 mm 

 long and was taken off North Carolina. The only 

 other illustrations of larval spotted seatrout were 

 of 3.0 and 5.0 mm SL fish from south Florida by 

 Jannke (1971). 



The first description of C. nebulosus eggs was by 

 Miles ( 1950, 1951 ). He stated that eggs measured 

 from 0.70 to 0.98 mm in diameter and contained 



one to four small oil globules. Later, Tabb (1966) 

 stated that eggs were spherical and normally had 

 one oil droplet, but sometimes two or three. 



In this paper, we provide detailed descriptions of 

 eggs and young larvae of spotted seatrout, based 

 on laboratory spawned and reared specimens. 



PROCEDURES 



Adult spotted seatrout were caught by hook and 

 line at Port Aransas, Tex., in August 1973. Eleven 

 fish (seven males and four females) were brought 

 into the laboratory and maintained in a 30,000-1 

 seawater tank. The tank was constructed of fiber 

 glass and measured 6 x 3 x 1.5 m. It contained 

 seawater which was recirculated through a shell- 

 and-gravel filter. 



The fish were fed shrimp and fish, both live and 

 dead. Temperature and photoperiod in the 

 laboratory were adjusted to simulate spring and, 

 subsequently, summer conditions. Spawning 

 began 1 mo after conditions were stabilized at 15 h 

 of light, 9 h of dark, and 26°C. Details of the 

 methods to induce spawning by spotted seatrout 

 are described by Arnold et al. (in press). In a 1-yr 

 period, the spotted seatrout have spawned during 

 each month for a total of 82 times. On several 

 occasions more than one female spawned. 



Eggs described in this paper were spawned by a 

 single female on 8 September 1975. They were 

 preserved hourly in S9c buffered Formalin^ from 



'Southeast Fisheries Center Port Aransas Laboratory, Na- 

 tional Marine Fisheries Service, NOAA, Port Aransas, TX 

 78373. 



Manuscript accepted March 1977. 



nSHERY BULLETIN: VOL. 76, NO. 1, 1978. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



65 



